Reduced self-heating in Si/SiGe field-effect transistors on thin virtual substrates prepared by low-energy plasma-enhanced chemical vapor deposition

This letter reports on the electrical performance of strained Si-based n-type heterostructure field-effect transistors prepared on 500 nm Si0.56Ge0.44 virtual substrates. The method of low-energy plasma-enhanced chemical vapor deposition at low temperature was used for the growth of the relaxed SiGe buffer. The active layers have been deposited by molecular-beam epitaxy. The thin buffer improves the thermal conductivity by a factor of 3 and shows a much lower surface roughness compared to control structures on conventional virtual substrate with a 5-mum-thick graded buffer. Cutoff frequencies of f(T)=55 GHz and f(max)(U)=138 GHz have been achieved which are very close to the results of the control sample.